1. Field of the Invention
The present invention relates to a pair of web pulling cylinders, particularly for use in printing machines. A single-layer or multiple-layer web is conveyed between the cylinders which are pressed together. The cylinders are driven and are in driven connection through drive elements mounted on the cylinder journals.
2. Description of the Related Art
German Patent 65 501 discloses a pair of pulling cylinders, wherein the cylinders are driven and are in driven connection through spur wheels mounted on the cylinder journals. The web is guided in a straight line through the cylinders which are adjusted relative to each other. If the web were simultaneously deflected or guided around one of the cylinders, when the web travels around the cylinder the speed increases on the upper side of the web which is guided around the cylinder corresponding to the increase of the radius resulting from the thickness of the web. The increase of the speed on the upper side of the web becomes greater as the number of the layers of the web increases. The speed difference relative to the second cylinder of the pair of pulling cylinders which rotates with unchanged web speed leads to the formation of creases and to displacement of the layers of the web. As a consequence, smearing of the print occurs within the layers of the web as well as on the surface thereof. In addition, the outer surfaces of the web become damaged because of a scratching effect of the rough outer surfaces of the cylinders.